U.S. patent application number 17/584251 was filed with the patent office on 2022-08-11 for tire.
This patent application is currently assigned to Sumitomo Rubber Industries, Ltd.. The applicant listed for this patent is Sumitomo Rubber Industries, Ltd.. Invention is credited to KEN TANIDA.
Application Number | 20220250413 17/584251 |
Document ID | / |
Family ID | |
Filed Date | 2022-08-11 |
United States Patent
Application |
20220250413 |
Kind Code |
A1 |
TANIDA; KEN |
August 11, 2022 |
TIRE
Abstract
A tire comprises a tread portion axially divided by
circumferential grooves into a first middle land portion, a crown
land portion and a second middle land portion. Each land portion
has a profile protruding radially outwardly from a reference tread
profile. The maximum protrusion amount of the second middle land
portion's profile is larger than the maximum protrusion amount of
the crown land portion's profile which is larger than the maximum
protrusion amount of the first middle land portion's profile.
Inventors: |
TANIDA; KEN; (Kobe-shi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Sumitomo Rubber Industries, Ltd. |
Hyogo |
|
JP |
|
|
Assignee: |
Sumitomo Rubber Industries,
Ltd.
Hyogo
JP
|
Appl. No.: |
17/584251 |
Filed: |
January 25, 2022 |
International
Class: |
B60C 11/00 20060101
B60C011/00; B60C 11/03 20060101 B60C011/03 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 9, 2021 |
JP |
2021-019221 |
Claims
1. A tire comprising a tread portion having a first tread edge to
be positioned inboard of a vehicle and a second tread edge to be
positioned outboard of the vehicle, wherein the tread portion is
provided with circumferential grooves extending continuously in the
tire circumferential direction to axially divide the tread portion
into land portions, the land portions include a crown land portion,
a first middle land portion adjacent to the crown land portion on
the first tread edge side thereof, and a second middle land portion
adjacent to the crown land portion on the second tread edge side
thereof, and in a meridian cross section of the tire under a normal
state of the tire, the crown land portion, the first middle land
portion and the second middle land portion respectively have a
crown profile, a first middle profile and a second middle profile
which protrude radially outwardly from respective reference tread
profiles, wherein a maximum protrusion amount of the first middle
profile from the reference tread profile therefor is larger than a
maximum protrusion amount of the crown profile from the reference
tread profile therefor which is larger than a maximum protrusion
amount of the second middle profile from the reference tread
profile therefor.
2. The tire according to claim 1, wherein the maximum protrusion
amount of each of the crown profile, the first middle profile and
the second middle profile is not more than 0.15 mm.
3. The tire according to claim 1, wherein the maximum protrusion
amount of the crown profile is in a range from 60% to 75% of the
maximum protrusion amount of the first middle profile.
4. The tire according to claim 2, wherein the maximum protrusion
amount of the crown profile is in a range from 60% to 75% of the
maximum protrusion amount of the first middle profile.
5. The tire according to claim 1, wherein the maximum protrusion
amount of the second middle profile is in a range from 25% to 40%
of the maximum protrusion amount of the first middle profile.
6. The tire according to claim 2, wherein the maximum protrusion
amount of the second middle profile is in a range from 25% to 40%
of the maximum protrusion amount of the first middle profile.
7. The tire according to claim 3, wherein the maximum protrusion
amount of the second middle profile is in a range from 25% to 40%
of the maximum protrusion amount of the first middle profile.
8. The tire according to claim 4, wherein the maximum protrusion
amount of the second middle profile is in a range from 25% to 40%
of the maximum protrusion amount of the first middle profile.
9. The tire according to claim 1, wherein each of the crown land
portion, the first middle land portion and the second middle land
portion is provided with lateral grooves arranged at 75 to 100
pitches over the circumference of the tire.
10. The tire according to claim 1, wherein the circumferential
grooves include a first shoulder circumferential groove positioned
on the most first tread edge side, and a second shoulder
circumferential groove positioned on the most second tread edge
side, and the maximum groove width of the second shoulder
circumferential groove is smaller than the maximum groove width of
the first shoulder circumferential groove.
11. The tire according to claim 3, wherein the circumferential
grooves include a first shoulder circumferential groove positioned
on the most first tread edge side, and a second shoulder
circumferential groove positioned on the most second tread edge
side, and the maximum groove width of the second shoulder
circumferential groove is smaller than the maximum groove width of
the first shoulder circumferential groove.
12. The tire according to claim 5, wherein the circumferential
grooves include a first shoulder circumferential groove positioned
on the most first tread edge side, and a second shoulder
circumferential groove positioned on the most second tread edge
side, and the maximum groove width of the second shoulder
circumferential groove is smaller than the maximum groove width of
the first shoulder circumferential groove.
13. The tire according to claim 7, wherein the circumferential
grooves include a first shoulder circumferential groove positioned
on the most first tread edge side, and a second shoulder
circumferential groove positioned on the most second tread edge
side, and the maximum groove width of the second shoulder
circumferential groove is smaller than the maximum groove width of
the first shoulder circumferential groove.
14. The tire according to claim 9, wherein the circumferential
grooves include a first shoulder circumferential groove positioned
on the most first tread edge side, and a second shoulder
circumferential groove positioned on the most second tread edge
side, and the maximum groove width of the second shoulder
circumferential groove is smaller than the maximum groove width of
the first shoulder circumferential groove.
15. The tire according to claim 10, wherein the maximum groove
width of the second shoulder circumferential groove is in a range
from 55% to 65% of the maximum groove width of the first shoulder
circumferential groove.
16. The tire according to claim 11, wherein the maximum groove
width of the second shoulder circumferential groove is in a range
from 55% to 65% of the maximum groove width of the first shoulder
circumferential groove.
17. The tire according to claim 12, wherein the maximum groove
width of the second shoulder circumferential groove is in a range
from 55% to 65% of the maximum groove width of the first shoulder
circumferential groove.
18. The tire according to claim 1, wherein each of the first middle
land portion and the second middle land portion is provided with
lateral grooves inclined at an angle of 10 to 30 degrees with
respect to the tire axial direction.
19. The tire according to claim 2, wherein each of the first middle
land portion and the second middle land portion is provided with
lateral grooves inclined at an angle of 10 to 30 degrees with
respect to the tire axial direction.
20. The tire according to claim 3, wherein each of the first middle
land portion and the second middle land portion is provided with
lateral grooves inclined at an angle of 10 to 30 degrees with
respect to the tire axial direction.
Description
FIELD OF THE INVENTION
[0001] The present disclosure relates to a tire, more particularly
to a tread pattern with land portions having different
profiles.
BACKGROUND ART
[0002] Patent Document 1 below discloses a tire in which the ground
contacting surface of a middle land portion protrudes radially
outwardly from a reference tread profile. Thereby, the contact
pressure acting on the circumferential edges on both sides of the
middle land portion is reduced to improve fuel efficiency and
braking performance on dry road surfaces. Patent Document 1:
Japanese Patent Application Publication No. 2020-111261
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0003] On the other hand, in order to fully derive designed
desirable performances from a tire, there has been proposed a tire
of which position on a vehicle is specified (namely, a tire
specified about which side of the tire is to be positioned inboard
of a vehicle).
When such a tire employs land portions of which ground contacting
surface protrudes radially outwardly from a reference tread profile
as disclosed in Patent Document 1, there is a tendency that uneven
wear occurs in a specific land portion.
[0004] The present disclosure was made in view of the above
problems, and a main object of the present disclosure is to provide
a tire in which uneven wear resistance is improved although the
position of the tire on a vehicle is specified.
Means for Solving the Problems
[0005] According to the present disclosure, a tire comprises a
tread portion having a first tread edge to be positioned inboard of
a vehicle and a second tread edge to be positioned outboard of the
vehicle, wherein
[0006] the tread portion is provided with circumferential grooves
extending continuously in the tire circumferential direction to
axially divide the tread portion into land portions,
[0007] the land portions include a crown land portion, a first
middle land portion adjacent to the crown land portion on the first
tread edge side thereof, and a second middle land portion adjacent
to the crown land portion on the second tread edge side thereof,
and
[0008] in a meridian cross section of the tire under a normal state
of the tire, the crown land portion, the first middle land portion
and the second middle land portion respectively have a crown
profile, a first middle profile and a second middle profile which
protrude radially outwardly from respective reference tread
profiles, wherein
[0009] a maximum protrusion amount of the first middle profile from
the reference tread profile therefor is larger than
[0010] a maximum protrusion amount of the crown profile from the
reference tread profile therefor which is larger than
[0011] a maximum protrusion amount of the second middle profile
from the reference tread profile therefor.
Effects of the Invention
[0012] In the tire according to the present disclosure, as the
maximum protrusion amounts are uniquely defined, the uneven wear
resistance of the tire can be improved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a developed partial view of the tread portion of a
tire as an embodiment of the present disclosure.
[0014] FIG. 2 is a schematic meridian cross-sectional view of the
tread portion shown in FIG. 1.
[0015] FIG. 3 is an enlarged cross-sectional view showing the crown
land portion, the first middle land portion, and the second middle
land portion shown in FIG. 2.
[0016] FIG. 4 is an enlarged view showing the crown land portion,
the first middle land portion, and the second middle land portion
shown in FIG. 1.
[0017] FIG. 5 is an enlarged view showing the first shoulder land
portion shown in FIG. 1.
[0018] FIG. 6 is an enlarged view showing the second shoulder land
portion shown in FIG. 2.
DETAILED DESCRIPTION OF THE INVENTION
[0019] An embodiment of the present disclosure will now be
described in detail in conjunction with accompanying drawings.
[0020] The present disclosure is suitably applied to pneumatic
tires, especially, winter tires for passenger cars although the
present disclosure is not limited to such intended end-usage and
pneumatic tires.
[0021] FIG. 1 is a developed partial view of a tread portion 2 of a
pneumatic tire 1 as an embodiment of the present disclosure.
[0022] As shown in FIG. 1, the tread portion 2 is provided with a
tread pattern asymmetric about the tire equator C, and the position
of the tire on a vehicle is specified about which side of the tire
is to be positioned inboard or outboard of the vehicle. Thus, the
tread portion 2 has a first tread edge T1 to be positioned inboard
of a vehicle, and a second tread edge T2 to be positioned outboard
of the vehicle.
The direction of the tire when mounted on the vehicle is indicated
in, for example, the sidewall portion (not shown) of the tire by
using characters and/or symbols.
[0023] The first tread edge T1 and the second tread edge T2 are the
axial outermost edges of the ground contacting patch of the tire
which occurs when the tire under its normal state is contacted with
a flat ground surface at a camber angle of 0 degree and loaded with
a normal tire load.
[0024] Here, the normal state is such that the tire is mounted on a
normal rim, and inflated to a normal pressure, but loaded with no
tire load.
[0025] In this application, dimensions, positions and the like
relating to the tire refer to those under the normal state unless
otherwise noted.
[0026] The normal rim is a wheel rim specified for the tire by a
standard included in a standardization system on which the tire is
based, for example, the "normal wheel rim" in JATMA, "Design Rim"
in TRA, and "Measuring Rim" in ETRTO. If there is no applicable
standard, a wheel rim recommended by the tire manufacturer is used
as the normal rim.
[0027] The normal pressure is air pressure specified for the tire
by a standard included in a standardization system on which the
tire is based, for example, the "maximum air pressure" in JATMA,
maximum value listed in the "TIRE LOAD LIMITS AT VARIOUS COLD
INFLATION PRESSURES" table in TRA, and "INFLATION PRESSURE" in
ETRTO. If there is no applicable standard, an air pressure
recommended by the tire manufacturer is used as the normal
pressure.
[0028] The normal tire load is a tire load specified for the tire
by a standard included in a standardization system on which the
tire is based, for example, the "maximum load capacity" in JATMA,
maximum value listed in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION
PRESSURES" table in TRA, and "LOAD CAPACITY" in ETRTO. If there is
no applicable standard, a maximum tire load specified by the tire
manufacturer is used as the normal tire load.
[0029] The tread portion 2 is provided with a plurality of
circumferential grooves 3 extending continuously in the tire
circumferential direction and positioned between the first tread
edge T1 and the second tread edge T2. By the circumferential
grooves 3, the tread portion 2 is axially divided into a plurality
of land portions 9.
[0030] The circumferential grooves 3 include a first crown
circumferential groove 4, a second crown circumferential groove 5,
a first shoulder circumferential groove 6, and a second shoulder
circumferential groove 7.
The first shoulder circumferential groove 6 is provided on the most
first tread edge T1 side among the circumferential grooves 3. The
second shoulder circumferential groove 7 is provided on the most
second tread edge T2 side among the circumferential grooves 3. The
first crown circumferential groove 4 is provided between the first
shoulder circumferential groove 6 and the tire equator C. The
second crown circumferential groove 5 is provided between the
second shoulder circumferential groove 7 and the tire equator
C.
[0031] The axial distance L1 from the tire equator C to the groove
center line of each of the first shoulder circumferential groove 6
and the second shoulder circumferential groove 7 is preferably set
in a range from 25% to 35% of the tread width TW.
[0032] The axial distance L2 from the tire equator C to the groove
center line of each of the first crown circumferential groove 4 and
the second crown circumferential groove 5 is preferably set in a
range from 5% to 15% of the tread width TW.
[0033] The tread width TW is the axial distance between the first
tread edge T1 and the second tread edge T2 measured under the
normal state.
[0034] In the present embodiment, each of the circumferential
grooves 3 extends straight in parallel with the tire
circumferential direction, or in a wavy shape in which the groove
center line slightly oscillates.
[0035] The groove width W1 of each of the circumferential grooves 3
is 3.0 mm or more, and preferably 3.0% to 7.0% of the tread width
TW.
[0036] In the present specification, the groove width of the
circumferential groove 3 is the distance between the groove edges
on both sides measured in the direction orthogonal to the groove
center line under the normal state. The groove edge is a boundary
between the groove and the ground contacting surface of the
adjacent land portion under the normal state.
[0037] The land portions 9 include a crown land portion 10, a first
middle land portion 11, and a second middle land portion 12. In
addition, the land portions 9 in the present embodiment include a
first shoulder land portion 13 and a second shoulder land portion
14.
[0038] The crown land portion 10 is defined between the first crown
circumferential groove 4 and the second crown circumferential
groove 5 and, in this present embodiment, disposed on the tire
equator C.
[0039] The first middle land portion 11 is defined between the
first crown circumferential groove 4 and the first shoulder
circumferential groove 6, and disposed adjacently to the crown land
portion 10 on the first tread edge T1 side.
[0040] The second middle land portion 12 is defined between the
second crown circumferential groove 5 and the second shoulder
circumferential groove 7, and disposed adjacently to the crown land
portion 10 on the second tread edge T2 side.
[0041] The first shoulder land portion 13 is defined between the
first shoulder circumferential groove 6 and the first tread edge
T1.
[0042] The second shoulder land portion 14 is defined between the
second shoulder circumferential groove 7 and the second tread edge
T2.
[0043] FIG. 2 is a meridian cross-sectional view including the tire
rotational axis schematically showing the tread portion 2 of the
tire 1 under the normal state.
[0044] As shown in FIG. 2, a tread profile of the tread portion 2
as a whole is curved convexly toward the radially outside.
[0045] FIG. 3 shows cross sections of the crown land portion 10,
the first middle land portion 11 and the second middle land portion
12.
[0046] As shown, the crown land portion 10, the first middle land
portion 11, and the second middle land portion 12 respectively have
a crown profile 45, a first middle profile 46, and a second middle
profile 47 which protrude radially outwardly from respective
reference tread profiles 44.
[0047] In FIG. 3, the curvatures of the crown profile 45, the first
middle profile 46, and the second middle profile 47 are
exaggeratingly shown as being larger than the actual curvatures for
easy understanding.
[0048] The reference tread profile 44 of the first middle land
portion 11 is a circular arc having a single radius and passing
through three positions which are both edges of the ground
contacting surface of the first middle land portion, and the groove
edge on the tire equator C side of a circumferential groove axially
inwardly adjacent to the first middle land portion 11 (namely, the
first crown circumferential groove 4 in the present
embodiment).
[0049] The reference tread profile 44 of the second middle land
portion 12 is a circular arc having a single radius and passing
through three positions which are both edges of the ground
contacting surface of the second middle land portion, and the
groove edge on the tire equator C side of a circumferential groove
axially inwardly adjacent to the second middle land portion 12
(namely, the second crown circumferential groove 5 in the present
embodiment).
[0050] The reference tread profile 44 of the crown land portion 10
is a circular arc which is one having a radius not smaller than the
other of the following two circular arcs: a first circular arc
having a single radius and passing through both edges of the ground
contacting surface of the crown land portion 10 and a groove edge
on the first tread edge T1 side of the first crown circumferential
groove 4; and
a second circular arc having a single radius and passing through
both edges of the ground contacting surface of the crown land
portion 10 and a groove edge on the second tread edge T2 side of
the second crown circumferential groove 5. In the present
embodiment, the first circular arc and the second circular arc have
the same radius.
[0051] According to the present disclosure, the maximum protrusion
amount d1 of the first middle profile 46 from the reference tread
profile 44 thereof is larger than the maximum protrusion amount d3
of the crown profile 45 from the reference tread profile 44
thereof, and
the maximum protrusion amount d3 of the crown profile 45 from the
reference tread profile 44 thereof is larger than the maximum
protrusion amount d2 of the second middle profile 47 from the
reference tread profile 44 thereof. Thereby, the tire 1 according
to the present disclosure can be improved in uneven wear resistance
performance. The reason for this is presumed as follows.
[0052] In the present disclosure, since the profile of each land
portion 9 protrudes from the reference tread profile 44, the
contact pressure acting on the circumferential edges of the land
portion 9 can be reduced, and uneven wear occurred near the
circumferential edges can be suppressed.
[0053] On the other hand, when the above profile is adopted in the
tread portion 2 for which the position on the vehicle is specified,
a land portion slightly inboard than the tire equator
(corresponding to the first middle land portion 11 in the present
embodiment) has a tendency to cause uneven wear. It is presumed
that this is because the above-mentioned land portion is subjected
to a relatively large ground pressure due to a slight negative
camber generally applied to vehicles.
[0054] According to the present disclosure, by setting the maximum
protrusion amounts of the profiles of the land portions 9 as
described above, the contact pressure acting on the circumferential
edges of the land portions 9 is adjusted in a well-balanced manner,
and in particular, uneven wear of the first middle land portion 11
can be effectively suppressed. As a result, the tire 1 according to
the present disclosure can exhibit excellent uneven wear resistance
performance.
[0055] Hereinafter, additional features of the tire 1 of the
present embodiment will be described in more detail. These features
are preferable, but not essential for the tire according to the
present disclosure.
[0056] It is preferable that, as shown in FIG. 1, the maximum
groove width W7 of the second shoulder circumferential groove 7 is
smaller than the maximum groove width W6 of the first shoulder
circumferential groove 6. Specifically, the maximum groove width W7
is set in a range from 55% to 65% of the maximum groove width
W6.
As a result, the air column resonance sound of the second shoulder
circumferential groove 7 having a large influence on noise
performance is reduced.
[0057] It is preferable that the maximum protrusion amount d3 of
the crown profile 45, the maximum protrusion amount d1 of the first
middle profile 46, and the maximum protrusion amount d2 of the
second middle profile 47 are not more than 0.15 mm.
As a result, uneven wear of a central portion in the tire axial
direction of each land portion can be suppressed.
[0058] The maximum protrusion amount d3 of the crown profile 45 is
preferably in a range from 60% to 75% of the maximum protrusion
amount d1 of the first middle profile 46.
The maximum protrusion amount d2 of the second middle profile 47 is
preferably in a range from 25% to 40% of the maximum protrusion
amount d1 of the first middle profile 46. As a result, the ground
contact pressure acting on each land portion becomes uniform, and
its uneven wear is suppressed.
[0059] As shown in FIG. 4, each of the crown land portion 10, the
first middle land portion 11, and the second middle land portion 12
is provided with lateral grooves extending in the tire axial
direction.
[0060] In each of the crown land portion 10, the first middle land
portion 11 and the second middle land portion 12, the number of
pitches applied for the same lateral grooves disposed at the
substantially same axial positions is, for example, 75 to 100,
preferably 80 to 90 when counted over the entire circumference of
the tire. As a result, uneven wear resistance and noise performance
are improved in a well-balanced manner.
[0061] The crown land portion 10 is provided with crown lateral
grooves 15.
[0062] The crown lateral grooves 15 extends across the entire axial
width of the crown land portion 10, and are inclined with respect
to the tire axial direction to a first direction (inclined downward
to the right in each drawing).
[0063] The crown lateral groove 15 comprises a first axial end
portion 16, a second axial end portion 17 and a central portion 18
extending therebetween. The groove width in the central portion 18
is smaller than the groove width in the first axial end portion 16
and smaller than the groove width in the second axial end portion
17.
[0064] In each of the crown lateral grooves 15, the maximum groove
width in the central portion 18 is not more than 15%, preferably 3%
to 15% of the maximum groove width in the first axial end portion
16 and the second axial end portion 17.
Preferably, the central portion 18 is configured as a narrow groove
portion having a groove width of not more than 1.5 mm. As a result,
the rigidity of the crown land portion 10 can be maintained, and
the steering stability on dry roads is improved.
[0065] Hereinafter, unless otherwise noted, the "narrow groove
portion" refers to a portion of a groove having a groove width of
not more than 1.5 mm; the "narrow groove" refers to a groove having
a groove width of not more than 1.5 mm over the entire length of
the groove; and a groove not described as a narrow groove has a
groove width larger than 1.5 mm.
[0066] In each lateral groove in the present embodiment, portions
not described as the narrow groove portion have groove widths of
about 2.0 to 4.0 mm, for example.
[0067] In the present embodiment, the central portions 18 of the
crown lateral grooves 15 extend across the center line in the tire
axial direction of the crown land portion 10.
In the present embodiment, the axial length L3 of each central
portion 18 is in a range from 40% to 60% of the axial width W2 of
the crown land portion 10. Such central portions 18 improve on-snow
performance and noise performance in a well-balanced manner.
[0068] The central portions 18 are inclined with respect to the
tire axial direction to the above-mentioned first direction. The
angle .theta.2 of each central portion 18 with respect to the tire
axial direction is not more than 45 degrees, preferably 35 to 45
degrees.
[0069] In each of the crown lateral grooves 15, the axial length of
the first axial end portion 16 and the axial length of the second
axial end portion 17 are smaller than the axial length L3 of the
central portion 18 and in a range from 20% to 30% of the axial
width W2 of the crown land portion 10.
[0070] The first axial end portion 16 and the second axial end
portion 17 are inclined with respect to the tire axial direction to
the first direction.
[0071] The angle of the first axial end portion 16 and the angle of
the second axial end portion 17 with respect to the tire axial
direction are smaller than the angle of the central portion 18 with
respect to the tire axial direction, and in a range from 10 to 25
degrees, for example.
It is preferable that, as a result of the above-described
configuration, the crown lateral groove 15 has a portion slightly
convex to one side in the tire circumferential direction which is
formed by the first axial end portion 16 and the central portion
18, and a portion slightly convex on the other side in the tire
circumferential direction which is formed by the second axial end
portion 17 and the central portion 18. By such configuration of the
crown lateral groove 15, the first axial end portion 16 and the
second axial end portion 17 can form hard compacted snow blocks
together with the circumferential grooves, and thereby the traction
performance when running on snow can be improved.
[0072] As the crown lateral groove 15 has the above-described
configuration, it is preferable that the inclination angle thereof
which is defined by the angle of a straight line drawn between both
ends of the crown lateral groove 15 is set to be not more than 45
degrees, more preferably 20 to 40 degrees with respect to the tire
axial direction.
[0073] Each of arrangement pitches P1 of the crown lateral grooves
15 in the tire circumferential direction is, for example, set in a
range from 60% to 90% of the axial width W2 of the crown land
portion 10. As a result, on-snow performance and noise performance
are improved in a well-balanced manner.
[0074] Between every two of the crown lateral grooves 15 adjacent
to each other in the tire circumferential direction, a first crown
narrow groove 23 and a second crown narrow groove 24 are
disposed.
The first crown narrow groove 23 extends from the first crown
circumferential groove 4 and is terminated within the crown land
portion 10. The second crown narrow groove 24 extends from the
second crown circumferential groove 5 and is terminated within the
crown land portion 10.
[0075] The axial length of the first crown narrow groove 23 is, for
example, set in a range from 80% to 120% of the axial length of the
first axial end portion 16 of the crown lateral groove 15.
In the present embodiment, the second crown narrow groove 24 is
terminated at an axial position on the first crown circumferential
groove 4 side of the axially inner end of the second axial end
portion 17 of the crown lateral groove 15. Such first crown narrow
grooves 23 and second crown narrow grooves 24 can disperse the
frequency spectrum of the noise generated when the crown land
portion 10 contacts with the ground, and improve the noise
performance.
[0076] The first crown narrow grooves 23 and the second crown
narrow grooves 24 are inclined with respect to the tire axial
direction to the above-mentioned first direction.
[0077] The angle of the first crown narrow groove 23 with respect
to the tire axial direction, and the angle of the second crown
narrow groove 24 with respect to the tire axial direction are
smaller than the angle of the central portion 18 of the crown
lateral groove 15 with respect to the tire axial direction.
[0078] In the present embodiment, the difference between the angles
of the first crown narrow groove 23 and the central portion 18, and
the difference between the angles of the second crown narrow groove
24 and the central portion 18, are not more than 15 degrees,
preferably not more than 10 degrees.
[0079] Each of the first crown narrow grooves 23 and the second
crown narrow grooves 24 is inclined at an angle of from 30 to 40
degrees with respect to the tire axial direction.
[0080] The first middle land portion 11 is provided with first
middle lateral grooves 20.
[0081] The first middle lateral grooves 20 extend across the entire
axial width of the first middle land portion 11, and inclined with
respect to the tire axial direction to a second direction opposite
to the first direction (inclined upward to the right in each
drawing).
[0082] With respect to the tire axial direction, the first middle
lateral grooves 20 are arranged at different angles than the crown
lateral grooves 15. Thereby, it is possible to prevent noises
generated by the lateral grooves 20 and 15 from resonating.
[0083] The angles of the first middle lateral grooves 20 with
respect to the tire axial direction are, for example, set in a
range from 10 to 30 degrees. Such first middle lateral grooves 20
help to further improve the noise performance.
[0084] In the present embodiment, in the plan view of the tread
portion, as shown in FIG. 1 and FIG. 4, the crown lateral grooves
15 and the first middle lateral grooves 20 are arranged such
that
an extension of a straight line drawn between both axial ends of
each crown lateral groove 15, and an extension of a straight line
drawn between both axial ends of one of the first middle lateral
grooves 20 which is axially adjacent to the each crown lateral
groove 15 intersect within the groove width of the first crown
circumferential groove 4.
[0085] More preferably, in the tire circumferential direction, the
opening width of the crown lateral groove 15 at the first crown
circumferential groove 4 overlaps with the opening width of the
first middle lateral groove 20 at the first crown circumferential
groove 4.
In other words, on both sides of the first crown circumferential
groove 4, the open ends of the crown lateral grooves 15 are
respectively aligned with the open ends of the first middle lateral
grooves 20. Thereby, the crown lateral grooves 15 and the first
middle lateral grooves 20 can form hard compacted snow blocks at
the intersections with the first crown circumferential groove 4,
and thereby, excellent on-snow performance may be exhibited.
[0086] In the present embodiment, the first middle land portion 11
is provided with first middle narrow grooves 26.
The first middle narrow grooves 26 extend across the entire axial
width of the first middle land portion 11, and are arranged in the
tire circumferential direction alternately with the first middle
lateral grooves 20.
[0087] In the present embodiment, the first middle narrow grooves
26 are inclined with respect to the tire axial direction to the
above-mentioned second direction.
The first middle narrow grooves 26 extend in substantially parallel
with the first middle lateral grooves 20 so that the angle
difference therebetween is not more than 5 degrees at any axial
position. The angle of the first middle narrow grooves 26 with
respect to the tire axial direction is smaller than the angle of
the first crown narrow grooves 23 and smaller than the angle of the
second crown narrow grooves 24. For example, the angle of the first
middle narrow grooves 26 with respect to the tire axial direction
is set in a range from 10 to 30 degrees.
[0088] The second middle land portion 12 is provided with second
middle lateral grooves 30 and second middle narrow grooves 31
alternately in the tire circumferential direction.
[0089] In the present embodiment, the second middle lateral grooves
30 extend across the entire axial width of the second middle land
portion 12, and are inclined with respect to the tire axial
direction to the second direction. It is preferable that the angles
of the second middle lateral grooves 30 with respect to the tire
axial direction are smaller than the angle of the central portions
18 of the crown lateral grooves 15 with respect to the tire axial
direction.
For example, the angles of the second middle lateral grooves 30 is
set in a range from 10 to 30 degrees with respect to the tire axial
direction. Thereby, it is possible to suppress the resonance of
noise generated by the second middle lateral grooves 30 with noise
generated by the crown lateral grooves 15.
[0090] In the present embodiment, the second middle lateral groove
30 comprises an axially inner groove portion 30a extending from the
second crown circumferential groove 5, and an axially outer narrow
groove portion 30b extending from the axially outer end of the
axially inner groove portion 30a to the second shoulder
circumferential groove 7.
[0091] In the present embodiment, the axially inner groove portion
30a extends across the center line in the tire axial direction of
the second middle land portion 12.
The axial length L4 of the axially inner groove portion 30a in this
example is in a range from 60% to 90% of the axial width W3 of the
second middle land portion 12. Such axially inner groove portions
30a can improve on-snow performance and uneven wear resistance in a
well-balanced manner.
[0092] In the present embodiment, it is preferable that, when each
of the axially inner groove portions 30a is virtually-extended
along the length direction thereof toward the crown land portion
10, the extension overlaps with the opening width of one of the
second crown circumferential grooves 5 at the crown lateral groove
15. Thereby, it is possible to further improve on-snow
performance.
[0093] In the present embodiment, the axially outer narrow groove
portion 30b extends linearly from the axially inner groove portion
30a to the second shoulder circumferential groove 7, while
inclining to the second direction.
[0094] In the present embodiment, the second middle narrow grooves
31 extend across the entire axial width of the second middle land
portion 12 and are inclined with respect to the tire axial
direction to the second direction. The second middle narrow grooves
31 extend in substantially parallel with the second middle lateral
grooves 30 so that the angle difference therebetween is not more
than 5 degrees at any axial position.
Such second middle narrow grooves 31 can improve on-snow
performance while suppressing uneven wear of the second middle land
portion 12.
[0095] As shown in FIG. 5, the first shoulder land portion 13 is
provided with first shoulder lateral grooves 35 and first shoulder
narrow grooves 36 alternately in the tire circumferential
direction.
[0096] In the present embodiment, the first shoulder lateral
grooves 35 extend from the first tread edge T1 to the first
shoulder circumferential groove 6. The first shoulder lateral
grooves 35 in this example are curved convexly toward one side in
the tire circumferential direction.
[0097] In the present embodiment, each of the first shoulder
lateral grooves 35 comprises a main portion 35a on the first tread
edge T1 side, and an axially inner end portion 35b extending from
the first shoulder circumferential groove 6 to the axially inner
end of the main portion 35a.
[0098] In the present embodiment, the main portion 35a extends
across the center line in the tire axial direction of the first
shoulder land portion 13. The axial length L5 of the main portion
35a in this example is in a range from 60% to 80% of the axial
width W4 of the first shoulder land portion 13. Thereby, it is
possible to improve on-snow performance and noise performance in a
well-balanced manner.
[0099] The groove width in the axially inner end portion 35b is
smaller than the groove width in the main portion 35a, and
preferably set in a range from 3% to 15% of the groove width in the
main portion 35a.
In the present embodiment, the axially inner end portion 35b is
configured as a narrow groove portion having a groove width of not
more than 1.5 mm. Thereby, the amount of air passing through the
first shoulder lateral grooves 35 is reduced, and as a result,
noise performance can be improved.
[0100] It is preferable that the axial length L6 of the axially
inner end portion 35b is smaller than the axial length L3 of the
central portion 18 of the crown lateral groove 15.
Specifically, the axial length L6 of the axially inner end portion
35b is in a range from 40% to 60% of the axial length L3 of the
central portion 18. Thereby, it is possible to suppress the
resonance of noise generated by the first shoulder lateral grooves
35 with noise generated by the crown lateral grooves 15.
[0101] In the present embodiment, the first shoulder narrow grooves
36 extends across the entire axial width of the first shoulder land
portion 13. The first shoulder narrow grooves 36 are curved
convexly toward one side in the tire circumferential direction.
Preferably, the first shoulder narrow grooves 36 extend in
substantially parallel with the first shoulder lateral grooves 35
so that the angle difference therebetween is not more than 5
degrees at any axial position. Such first shoulder narrow grooves
36 can improve on-snow performance while suppressing uneven wear of
the first shoulder land portion 13.
[0102] As shown in FIG. 6, the second shoulder land portion 14 is
provided with second shoulder lateral grooves 40 and second
shoulder narrow grooves 41 alternately in the tire circumferential
direction.
[0103] The second shoulder lateral grooves 40 extend axially
inwardly from the second tread edge T2 and are terminated within
the second shoulder land portion 14. In the present embodiment, the
axial length L7 of the second shoulder lateral grooves 40 is in a
range from 75% to 90% of the axial width W5 of the second shoulder
land portion 14. Thereby, the air in the second shoulder
circumferential groove 7 is prevented from flowing out toward the
second tread edge T2. Thus, it is possible to prevent the noise
performance from deteriorating.
[0104] In the present embodiment, the second shoulder lateral
groove 40 comprises a main portion 40a on the second tread edge T2
side, and an axially inner end portion 40b extending axially
inwardly from the axially inner end of the main portion 40a. The
groove width in the axially inner end portion 40b is smaller than
the groove width in the main portion 40a.
[0105] In the present embodiment, the main portions 40a of the
second shoulder lateral grooves 40 extend across the center line in
the tire axial direction of the second shoulder land portion
14.
The axial length L8 of the main portion 40a is set in a range from
60% to 70% of the axial width W5 of the second shoulder land
portion 14. Thereby, on-snow performance and noise performance can
be improved in a well-balanced manner.
[0106] In the present embodiment, the axially inner end portion 40b
extends axially inwardly from the main portion 40a and is
terminated within the second shoulder land portion 14.
The axial length L9 of the axially inner end portion 40b is in a
range from 15% to 25% of the axial width W5 of the second shoulder
land portion 14. Preferably, the axial length L9 is smaller than
the axial length L3 of the central portion 18 of the crown lateral
groove 15. Thereby, it is possible to prevent noise generated by
the second shoulder lateral grooves 40 from resonating with noise
generated by the crown lateral groove 15.
[0107] In the second shoulder lateral grooves 40, the groove width
in the axially inner end portion 40b is preferably set in a range
from 3% to 15% of the groove width in the main portion 40a.
In the present embodiment, the axially inner end portion 40b is
configured as a narrow groove portion having a groove width of not
more than 1.5 mm. Thereby, it is possible to obtain excellent
steering stability on dry roads.
[0108] In the present embodiment, the second shoulder narrow
grooves 41 extend across the entire axial width of the second
shoulder land portion 14. In the present embodiment, the second
shoulder narrow grooves 41 extend in substantially parallel with
the second shoulder lateral grooves 40 so that the angle difference
therebetween is not more than 5 degrees at any axial position.
[0109] While detailed description has been made of a preferable
embodiment of the present disclosure, the present disclosure can be
embodied in various forms without being limited to the illustrated
embodiment.
Comparison Tests
[0110] Pneumatic tires of size 225/65R17 having the tread pattern
shown in FIG. 1 were experimentally manufactured as test tires
(Working example tires Ex 1-Ex 10 and Comparative example tire Ref)
by changing only the maximum protrusion amounts d1, d2 and d3 as
shown in Table 1.
The test tires mounted on wheel rims of size 17.times.7.0J (tire
pressure: front 230 kPa, rear 210 kPa) were attached to a test car
(1600 cc front wheel drive passenger car) and tested for uneven
wear resistance and noise performance as follows.
21 Uneven Wear Resistance Test>
[0111] The test car was traveled for a predetermined distance and
then the tread portion was visually checked for the wear condition
especially of the first middle land portion and therearound. The
results are indicated in Table 1 by an index based on Comparative
example Ref being 100, wherein the larger the value, the better the
uneven wear resistance.
<Noise Performance Test>
[0112] During the test car was running on a dry asphalt road
surface, noise was evaluated by the test driver, The results are
indicated in Table 1 by an index based on Comparative example Ref
being 100, wherein the larger the value, the better the noise
performance.
TABLE-US-00001 TABLE 1 Tire Ref Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5
maximum protrusion amount 0.10 0.15 0.15 0.15 0.15 0.15 first
middle profile d1 (mm) second middle profile d2 (mm) 0.10 0.05 0.03
0.04 0.06 0.07 d2/d1 (%) 100 33 20 27 40 47 crown profile d3 (mm)
0.10 0.10 0.08 0.09 0.11 0.12 d3/d1 (%) 100 67 53 60 73 80 uneven
wear resistance 100 110 108 109 110 109 noise performance 100 115
117 116 113 111 Tire Ex. 6 Ex. 7 Ex. 8 Ex. 9 Ex. 10 maximum
protrusion amount 0.25 0.25 0.25 0.25 0.25 first middle profile d1
(mm) second middle profile d2 (mm) 0.04 0.06 0.08 0.10 0.12 d2/d1
(%) 16 24 32 40 48 crown profile d3 (mm) 0.14 0.16 0.18 0.20 0.22
d3/d1 (%) 56 64 72 80 88 uneven wear resistance 108 109 110 110 108
noise performance 118 117 116 114 111
[0113] From the test results, it was confirmed that the tires
according to the present disclosure exhibited excellent uneven wear
resistance and excellent noise performance.
Statement of the Present Disclosure
[0114] The present disclosure is as follows: Disclosure 1: A tire
comprising a tread portion having a first tread edge to be
positioned inboard of a vehicle and a second tread edge to be
positioned outboard of the vehicle, wherein
[0115] the tread portion is provided with circumferential grooves
extending continuously in the tire circumferential direction to
axially divide the tread portion into land portions,
[0116] the land portions include
a crown land portion, a first middle land portion adjacent to the
crown land portion on the first tread edge side thereof, and a
second middle land portion adjacent to the crown land portion on
the second tread edge side thereof, and
[0117] in a meridian cross section of the tire under a normal state
of the tire, the crown land portion, the first middle land portion
and the second middle land portion respectively have a crown
profile, a first middle profile and a second middle profile which
protrude radially outwardly from respective reference tread
profiles, wherein
[0118] a maximum protrusion amount of the first middle profile from
the reference tread profile therefor is larger than
[0119] a maximum protrusion amount of the crown profile from the
reference tread profile therefor which is larger than
[0120] a maximum protrusion amount of the second middle profile
from the reference tread profile therefor.
Disclosure 2: The tire according to Disclosure 1, wherein
[0121] the maximum protrusion amount of each of the crown profile,
the first middle profile and the second middle profile is not more
than 0.15 mm.
Disclosure 3: The tire according to Disclosure 1 or 2, wherein
[0122] the maximum protrusion amount of the crown profile is in a
range from 60% to 75% of the maximum protrusion amount of the first
middle profile.
Disclosure 4: The tire according to Disclosure 1, 2 or 3,
wherein
[0123] the maximum protrusion amount of the second middle profile
is in a range from 25% to 40% of the maximum protrusion amount of
the first middle profile.
Disclosure 5: The tire according to Disclosure 1, 2, 3 or 4,
wherein
[0124] each of the crown land portion, the first middle land
portion and the second middle land portion is provided with lateral
grooves arranged at 75 to 100 pitches over the circumference of the
tire.
Disclosure 6: The tire according to any one of Disclosures 1 to 5,
wherein
[0125] the circumferential grooves include a first shoulder
circumferential groove positioned on the most first tread edge
side, and a second shoulder circumferential groove positioned on
the most second tread edge side, and
[0126] the maximum groove width of the second shoulder
circumferential groove is smaller than the maximum groove width of
the first shoulder circumferential groove.
Disclosure 7: The tire according to Disclosure 6, wherein
[0127] the maximum groove width of the second shoulder
circumferential groove is in a range from 55% to 65% of the maximum
groove width of the first shoulder circumferential groove.
Disclosure 8: The tire according to any one of Disclosures 1 to 7,
wherein
[0128] each of the first middle land portion and the second middle
land portion is provided with lateral grooves inclined at an angle
of 10 to 30 degrees with respect to the tire axial direction.
DESCRIPTION OF THE REFERENCE SIGNS
[0129] 2 tread portion
[0130] 3 circumferential groove
[0131] 9 land portion
[0132] 10 crown land portion
[0133] 11 first middle land portion
[0134] 12 second middle land portion
[0135] 44 reference tread profile
[0136] 45 crown profile
[0137] 46 first middle profile
[0138] 47 second middle profile
[0139] T1 first tread edge
[0140] T2 second tread edge
* * * * *